Manual for mount - man 8 mount

MOUNT(8) Linux Programmer's Manual MOUNT(8)
NAMEmount(2,8) - mount(2,8) a file(1,n)systemSYNOPSISmount(2,8) [-lhV]mount(2,8) -a [-fFnrsvw] [-t vfstype] [-O optlist]mount(2,8) [-fnrsvw] [-o options[,...]] device| dirmount(2,8) [-fnrsvw] [-t vfstype] [-o options] devicedirDESCRIPTION
All files accessible in(1,8) a Unix system are arranged in(1,8) one big tree, the
file(1,n) hierarchy, rooted at/. These files can be spread out over sev-
eral devices. The mount(2,8)command serves to attach the file(1,n)system found
on some device to the big file(1,n) tree. Conversely, the umount(8) command
will detach it again.
The standard form of the mount(2,8)command, is
mount(2,8) -t typedevicedir
This tells the kernel to attach the file(1,n)system found on device (which
is of typetype) at the directory dir. The previous contents (if(3,n) any)
and owner and mode of dir become invisible, and as long as this file(1,n)system remains mounted, the pathname dir refers to the root of the file(1,n)system on device.
Three forms of invocation do not actually mount(2,8) anything:
mount(2,8) -h
prints a helpmessage;
mount(2,8) -V
prints a version(1,3,5)string(3,n); and just
mount(2,8) [-l] [-t type]
lists all mounted file(1,n) systems (of typetype). The option -l adds the
(ext2, ext3 and XFS) labels in(1,8) this listing. See below.
Since Linux 2.4.0 it is possible to remount part of the file(1,n) hierarchy
somewhere else. The call is
mount(2,8) --bind olddir newdir
After this call the same contents is accessible in(1,8) two places. One can
also remount a single file(1,n) (on a single file(1,n)).
This call attaches only (part of) a single filesystem, not possible
submounts. The entire file(1,n) hierarchy including submounts is attached a
second place using
mount(2,8) --rbind olddir newdir
Note that the filesystem mount(2,8)options will remain the same as those on
the original mount(2,8) point, and cannot be changed by passing the -o
option along with --bind/--rbind.
Since Linux 2.5.1 it is possible to atomically move(3x,7,3x curs_move) a mounted tree to
another place. The call is
mount(2,8) --move olddir newdir
The proc(5,n)file(1,n)system is not associated with a special device, and when
mounting it, an arbitrary keyword, such asproc(5,n) can be used instead of
a device specification. (The customary choice none is less(1,3) fortunate:
the error(8,n)message `none busy' from umountcan be confusing.)
Most devices are indicated by a file(1,n) name (of a block special device),
like /dev/sda1, but there are other possibilities. For example, in(1,8) the
case of an NFS mount(2,8), device may look(1,8,3 Search::Dict) like knuth.cwi.nl:/dir. It is
possible to indicate a block special device using its volume label or
UUID (see the -L and -U options below).
The file(1,n)/etc/fstab (see fstab(5)), may contain lines describing what
devices are usually mounted where, using which options. This file(1,n) is
used in(1,8) three ways:
(i) The commandmount(2,8) -a [-t type] [-O optlist]
(usually given in(1,8) a bootscript) causes all file(1,n) systems mentioned in(1,8)fstab (of the proper type and/or having or not having the proper
options) to be mounted as indicated, except for those whose line con-
tains the noauto keyword. Adding the -F option will makemount(2,8)fork, so
that the filesystems are mounted simultaneously.
(ii) When mounting a file(1,n)system mentioned in(1,8)fstab, it suffices to
give only the device, or only the mount(2,8) point.
(iii) Normally, only the superuser can mount(2,8)file(1,n) systems. However,
when fstab contains the user option on a line, anybody can mount(2,8) the
corresponding system.
Thus, given a line/dev/cdrom /cd iso9660 ro,user,noauto,unhide
any user can mount(2,8) the iso9660 file(1,n)system found on his CDROM using the
commandmount(2,8) /dev/cdrom
or
mount(2,8) /cd
For more details, see fstab(5). Only the user that mounted a filesys-
tem can unmount it again. If any user should be able to unmount, then
use users(1,5)instead of user in(1,8) the fstab line. The owner option is simi-
lar to the user option, with the restriction that the user must be the
owner of the special file. This may be useful e.g. for/dev/fdif(3,n) a
login(1,3,5)script makes the console(4,n) user owner of this device. The groupoption is similar, with the restriction that the user must be member of
the group of the special file.
The programs mount(2,8)and umountmaintain a list of currently mounted file(1,n)
systems in(1,8) the file(1,n)/etc/mtab. If no arguments are given to mount(2,8),
this list is printed.
When the proc(5,n) filesystem is mounted (say at/proc(5,n)), the files /etc/mtab
and /proc(5,n)/mounts have very similar contents. The former has somewhat
more information, such as the mount(2,8)options used, but is not necessar-
ily up-to-date (cf. the -n option below). It is possible to replace/etc/mtab by a symbolic link(1,2) to /proc(5,n)/mounts, and especially when you
have very large numbers of mounts things will be much faster with that
symlink, but some information is lost that way, and in(1,8) particular work-
ing with the loop device will be less(1,3) convenient, and using the "user"
option will fail.
OPTIONS
The fullset(7,n,1 builtins) of options used by an invocation of mount(2,8)is determined by
first extracting the optionsfor the file(1,n)system from the fstab table,
then applying any options specified by the -o argument, and finally
applying a -r or -w option, when present.
Options available for the mount(2,8)command:
-V Output version.
-h Print a help message.
-v Verbose mode.
-a Mount all filesystems (of the given types) mentioned in(1,8)fstab.-F (Used in(1,8) conjunction with -a.) Fork off a new incarnation of
mount(2,8)for each device. This will do the mounts on different
devices or different NFS serversin(1,8) parallel. This has the
advantage that it is faster; also NFS timeouts go in(1,8) parallel. A
disadvantage is that the mounts are done in(1,8) undefined order.
Thus, you cannot use this optionif(3,n) you want to mount(2,8) both /usr
and /usr/spool.-f Causes everything to be done except for the actual systemcall;
if(3,n) it's not obvious, this ``fakes'' mounting the file(1,n) system.
This option is useful in(1,8) conjunction with the -v flag to deter-
mine what the mount(2,8)command is trying to do. It can also be used
to add entries for devices that were mounted earlier with the -n
option.
-i Don't call the /sbin/mount.<filesystem> helper even if(3,n) it
exists.
-l Add the ext2, ext3 and XFS labels in(1,8) the mount(2,8) output. Mount
must have permission to read(2,n,1 builtins) the disk device (e.g. be suid root)
for this to work. One can set(7,n,1 builtins) such a labelfor ext2 or ext3
using the e2label(8) utility, or for XFS using xfs_admin(8), or
forreiserfs using reiserfstune(8).-n Mount without writing in(1,8)/etc/mtab. This is necessary for exam-
ple when /etc is on a read-only file(1,n) system.
-p num In case of a loop mount(2,8) with encryption, read(2,n,1 builtins) the passphrase
from file(1,n) descriptor num instead of from the terminal.
-s Tolerate sloppy mount(2,8)options rather than failing. This will
ignore mount(2,8)options not supported by a filesystem type. Not all
filesystems support this option. This option exists for support
of the Linux autofs-based automounter.
-r Mount the file(1,n)system read-only. A synonym is -o ro.-w Mount the file(1,n)systemread(2,n,1 builtins)/write. This is the default. A synonym
is -o rw.-L label
Mount the partition that has the specified label.-U uuid
Mount the partition that has the specified uuid. These two
options require the file(1,n)/proc(5,n)/partitions (present since Linux
2.1.116) to exist.
-t vfstype
The argument following the -t is used to indicate the file(1,n)sys-
tem type. The file(1,n)system types which are currently supported
include: adfs, affs, autofs, coda, coherent, cramfs, devpts,
efs, ext, ext2, ext3, hfs, hpfs, iso9660, jfs, minix, msdos,
ncpfs, nfs, ntfs, proc(5,n), qnx4, ramfs, reiserfs, romfs, smbfs,
sysv, tmpfs, udf, ufs, umsdos, usbfs, vfat, xenix, xfs, xiafs.
Note that coherent, sysv and xenix are equivalent and that xenix
and coherent will be removed at some point in(1,8) the future -- use
sysv instead. Since kernel version(1,3,5) 2.1.21 the types ext and
xiafs do not exist anymore. Earlier, usbfs was known asusbde-vfs.
For most types all the mount(2,8)program has to do is issue a simple
mount(2,8)(2) systemcall, and no detailed knowledge of the filesys-
tem type is required. For a few types however (like nfs, smbfs,
ncpfs) ad hoc code is necessary. The nfs ad hoc code is built
in(1,8), but smbfs and ncpfs have a separate mount(2,8) program. In order
to make it possible to treat all types in(1,8) a uniform way, mount(2,8)
will execute the program /sbin/mount.TYPE (if(3,n) that exists) when
called with typeTYPE. Since various versions of the smbmount
program have different calling conventions, /sbin/mount.smbfs
may have to be a shell script that sets up the desired call.
If no -t option is given, or if(3,n) the auto(5,8)type is specified,
mount(2,8) will try to guess the desired type. If mount(2,8) was compiled
with the blkidlibrary, the guessing is done by this library.
Otherwise, mount(2,8) guesses itself by probing the superblock; if(3,n)
that does not turn up anything that looks familiar, mount(2,8) will
try to read(2,n,1 builtins) the file(1,n)/etc/filesystems, or, if(3,n) that does not
exist, /proc(5,n)/filesystems. All of the filesystem types listed
there will be tried, except for those that are labeled "nodev"
(e.g., devpts, proc(5,n) and nfs). If /etc/filesystems ends in(1,8) a
line with a single * only, mount(2,8) will read(2,n,1 builtins)/proc(5,n)/filesystems
afterwards.
The auto(5,8)type may be useful for user-mounted floppies. Creating
a file(1,n)/etc/filesystems can be useful to change the probe order
(e.g., to try vfat before msdos or ext3 before ext2) or if(3,n) you
use a kernel module autoloader. Warning: the probing uses a
heuristic (the presence of appropriate `magic(4,5)'), and could rec-
ognize the wrong filesystem type, possibly with catastrophic
consequences. If your data is valuable, don't ask mount(2,8)to
guess.
More than one type may be specified in(1,8) a comma separated list.
The list of file(1,n)system types can be prefixed with no to specify
the file(1,n)system types on which no action should be taken. (This
can be meaningful with the -a option.)
For example, the command:
mount(2,8) -a -t nomsdos,ext
mounts all file(1,n) systems except those of typemsdos and ext.-O Used in(1,8) conjunction with -a, to limit the set(7,n,1 builtins) of filesystems to
which the -a is applied. Like -t in(1,8) this regard except that it
is useless except in(1,8) the context of -a. For example, the com-
mand:
mount(2,8) -a -O no_netdev
mounts all file(1,n) systems except those which have the option_net-dev specified in(1,8) the options field in(1,8) the /etc/fstab file.
It is different from -t in(1,8) that each option is matched exactly;
a leading no at the beginning of one option does not negate the
rest.
The -t and -O options are cumulative in(1,8) effect; that is, the
commandmount(2,8) -a -t ext2 -O _netdev
mounts all ext2 filesystems with the _netdev option, not all
filesystems that are either ext2 or have the _netdev option
specified.
-o Options are specified with a -o flag followed by a comma sepa-
rated string(3,n) of options. Some of these options are only useful
when they appear in(1,8) the /etc/fstab file. The following options
apply to any file(1,n)system that is being mounted (but not every
file(1,n)system actually honors them - e.g., the sync(1,2,8)option today
has effect only for ext2, ext3 and ufs):async All I/O to the file(1,n)system should be done asynchronously.
atime Update inode access(2,5)time(1,2,n)for each access. This is the
default.
auto(5,8)Can be mounted with the -a option.
defaults
Use default options: rw, suid, dev, exec(3,n,1 builtins), auto(5,8), nouser,
and async.dev Interpret character or block special devices on the file(1,n)
system.
exec(3,n,1 builtins)Permit execution of binaries.
groupAllow an ordinary (i.e., non-root) user to mount(2,8) the file(1,n)systemif(3,n) one of his groups matches the group of the
device. This option implies the optionsnosuid and nodev
(unless overridden by subsequent options, asin(1,8) the
optionlinegroup,dev,suid).mand Allow mandatory locks on this filesystem. See fcntl(2)._netdev
The filesystem resides on a device that requires network
access(2,5) (used to prevent the system from attempting to
mount(2,8) these filesystems until the network has been
enabled on the system).noatime
Do not update(7,n) inode access(2,5)times on this file(1,n)system
(e.g, for faster access(2,5) on the news spool to speed up
news servers).noauto Can only be mounted explicitly (i.e., the -a option will
not cause the file(1,n)system to be mounted).nodev Do not interpret character or block special devices on
the file(1,n) system.
noexec Do not allow direct execution of any binaries on the
mounted file(1,n) system. (Until recently it was possible to
run binaries anyway using a command like /lib/ld(1,8)*.so
/mnt/binary. This trick fails since Linux 2.4.25 /
2.6.0.)
nomand Do not allow mandatory locks on this filesystem.
nosuid Do not allow set-user-identifier or set-group-identifier
bits to take effect. (This seems safe, but is in(1,8) fact
rather unsafe if(3,n) you have suidperl(1) installed.)
nouser Forbid an ordinary (i.e., non-root) user to mount(2,8) the
file(1,n) system. This is the default.
owner Allow an ordinary (i.e., non-root) user to mount(2,8) the file(1,n)systemif(3,n) he is the owner of the device. This option
implies the optionsnosuid and nodev (unless overridden
by subsequent options, asin(1,8) the optionlineowner,dev,suid).remount
Attempt to remount an already-mounted file(1,n) system. This
is commonly used to change the mount(2,8) flags for a file(1,n)system, especially to make a readonlyfile(1,n)system write-
able. It does not change device or mount(2,8) point.
ro Mount the file(1,n)system read-only.
rw Mount the file(1,n)system read-write.
suid Allow set-user-identifier or set-group-identifier bits to
take effect.
sync(1,2,8)All I/O to the file(1,n)system should be done synchronously.
dirsync
All directory updates within the file(1,n)system should be
done synchronously. This affects the following system
calls: creat, link(1,2), unlink(1,2), symlink, mkdir(1,2), rmdir(1,2), mknod(1,2)
and rename.
user Allow an ordinary user to mount(2,8) the file(1,n) system. The
name of the mounting user is written to mtab so that he
can unmount the file(1,n)system again. This option implies
the optionsnoexec, nosuid, and nodev (unless overridden
by subsequent options, asin(1,8) the optionlineuser,exec(3,n,1 builtins),dev,suid).users(1,5)Allow every user to mount(2,8) and unmount the file(1,n) system.
This option implies the optionsnoexec, nosuid, and nodev
(unless overridden by subsequent options, asin(1,8) the
optionlineusers(1,5),exec(3,n,1 builtins),dev,suid).--bind Remount a subtree somewhere else (so that its contents are
available in(1,8) both places). See above.
--move Move a subtree to some other place. See above.
FILESYSTEM SPECIFIC MOUNT OPTIONS
The following options apply only to certain file(1,n) systems. We sort(1,3) them
by file(1,n) system. They all follow the -o flag.
What options are supported depends a bit on the running kernel. More
info(1,5,n) may be found in(1,8) the kernel source subdirectory Documenta-tion/filesystems.Mount optionsfor adfsuid=value and gid=value
Set the owner and group of the files in(1,8) the file(1,n)system
(default: uid=gid=0).ownmask=value and othmask=value
Set the permission mask for ADFS 'owner' permissions and 'other'
permissions, respectively (default: 0700 and 0077, respec-
tively). See also /usr/src/linux/Documentation/filesys-tems/adfs.txt.Mount optionsfor affsuid=value and gid=value
Set the owner and group of the root of the file(1,n)system (default:
uid=gid=0, but with optionuid or gid without specified value,
the uid and gid of the current process are taken).setuid=value and setgid=value
Set the owner and group of all files.
mode=value
Set the mode of all files to value & 0777 disregarding the orig-
inal permissions. Add search permission to directories that
have read(2,n,1 builtins) permission. The value is given in(1,8) octal.
protect
Do not allow any changes to the protection bits on the file(1,n) sys-
tem.
usemp Set uid and gid of the root of the file(1,n)system to the uid and
gid of the mount(2,8) point upon the first sync(1,2,8) or umount, and then
clear(1,3x,3x clrtobot) this option. Strange...
verbose
Print an informational messagefor each successful mount.
prefix=string(3,n)
Prefix used before volume name, when following a link.
volume=string(3,n)
Prefix (of length atmost 30) used before '/' when following a
symbolic link.
reserved=value
(Default: 2.) Number of unused blocks at the start of the
device.
root=value
Give explicitly the location of the root block.
bs=value
Give blocksize. Allowed values are 512, 1024, 2048, 4096.
grpquota / noquota / quota(1,8)/ usrquota
These options are accepted but ignored. (However, quota(1,8) utili-
ties may react to such stringsin(1,8)/etc/fstab.)
Mount optionsfor coherent
None.
Mount optionsfor devpts
The devpts file(1,n)system is a pseudo file(1,n)system, traditionally mounted
on /dev/pts. In order to acquire a pseudo terminal, a process opens
/dev/ptmx; the number of the pseudo terminal is then made available to
the process and the pseudo terminal slave can be accessed as/dev/pts/<number>.uid=value and gid=value
This sets the owner or the group of newly created PTYs to the
specified values. When nothing is specified, they will be set(7,n,1 builtins) to
the UID and GID of the creating process. For example, if(3,n) there
is a tty(1,4)group with GID 5, then gid=5 will cause newly created
PTYs to belong to the tty(1,4) group.
mode=value
Set the mode of newly created PTYs to the specified value. The
default is 0600. A value of mode=620 and gid=5 makes "mesg y"
the default on newly created PTYs.
Mount optionsfor ext
None. Note that the `ext' file(1,n)system is obsolete. Don't use it.
Since Linux version(1,3,5) 2.1.21 extfs is no longer part of the kernel
source.
Mount optionsfor ext2
The `ext2' file(1,n)system is the standard Linux file(1,n) system. Since Linux
2.5.46, formostmount(2,8)options the default is determined by the
filesystem superblock. Set them with tune2fs(8).acl/ noacl
Support POSIXAccess Control Lists (or not).bsddf / minixdf
Set the behaviour for the statfssystem call. The minixdf behav-
iour is to returnin(1,8) the f_blocks field the total number of
blocks of the file(1,n)system, while the bsddf behaviour (which is
the default) is to subtract the overhead blocks used by the ext2
file(1,n)system and not available forfile(1,n) storage. Thus
% mount(2,8) /k -o minixdf; df /k; umount /k
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/sda6 2630655 86954 2412169 3% /k
% mount(2,8) /k -o bsddf; df /k; umount /k
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/sda6 2543714 13 2412169 0% /k
(Note that this example shows that one can add commandlineoptions to
the options given in(1,8)/etc/fstab.)
check Check filesystem (block and inode bitmaps) atmount(2,8) time.
check=none/ nocheck
No checking is done atmount(2,8) time. This is the default. This is
fast. It is wise to invokee2fsck(8) every now and then, e.g.
atboot time.
debug Print debugging info(1,5,n) upon each (re)mount.
errors=continue/ errors=remount-ro / errors=panic
Define the behaviour when an error(8,n) is encountered. (Either
ignore errors and just mark the file(1,n)system erroneous and con-
tinue, or remount the file(1,n)system read-only, or panic and halt
the system.) The default is set(7,n,1 builtins)in(1,8) the filesystem superblock,
and can be changed using tune2fs(8).grpid or bsdgroups / nogrpid or sysvgroups
These options define what groupid a newly created file(1,n) gets.
When grpid is set(7,n,1 builtins), it takes the groupid of the directory in(1,8)which it is created; otherwise (the default) it takes the fsgid
of the current process, unless the directory has the setgid bit
set(7,n,1 builtins), in(1,8)whichcase it takes the gid from the parent directory,
and also gets(3,n) the setgid bit set(7,n,1 builtins)if(3,n) it is a directory itself.
grpquota / noquota / quota(1,8)/ usrquota
These options are accepted but ignored.
nobh Do not attach buffer_heads to file(1,n) pagecache. (Since 2.5.49.)
nouid32
Disables 32-bit UIDs and GIDs. This is for interoperability
with older kernels which only store and expect 16-bit values.
oldalloc or orlov
Use old allocator or Orlov allocator for new inodes. Orlov is
default.
resgid=n and resuid=n
The ext2 file(1,n)system reserves a certain percentage of the avail-
able space (by default 5%, see mke2fs(8) and tune2fs(8)). These
options determine who can use the reserved blocks. (Roughly:
whoever has the specified uid, or belongs to the specified
group.)
sb=n Instead of block 1, use block nas superblock. This could be
useful when the filesystem has been damaged. (Earlier, copies
of the superblock would be made every 8192 blocks: in(1,8) block 1,
8193, 16385, ... (and one got thousands of copies on a big
filesystem). Since version(1,3,5) 1.08, mke2fshas a -s (sparse
superblock) option to reduce the number of backup superblocks,
and since version(1,3,5) 1.15 this is the default. Note that this may
mean that ext2 filesystems created by a recent mke2fscannot be
mounted r/w under Linux 2.0.*.) The block number here uses 1k
units. Thus, if(3,n) you want to use logical block 32768 on a
filesystem with 4k blocks, use "sb=131072".user_xattr / nouser_xattr
Support "user." extended attributes (or not).Mount optionsfor ext3
The `ext3' file(1,n)system is a version(1,3,5) of the ext2 file(1,n)systemwhich has
been enhanced with journalling. It supports the same optionsas ext2
as well as the following additions:
journal=update(7,n)
Update the ext3 file(1,n)system's journal to the current format.
journal=inum
When a journal already exists, this option is ignored. Other-
wise, it specifies the number of the inode which will represent
the ext3 file(1,n)system's journal file(1,n); ext3 will create a new
journal, overwriting the old contents of the file(1,n) whose inode
number is inum.noload Do not load(7,n) the ext3 file(1,n)system's journal on mounting.
data=journal / data=ordered / data=writeback
Specifies the journalling mode forfile(1,n) data. Metadata is
always journaled. To use modes other than ordered on the rootfile(1,n)system, pass the mode to the kernel asboot parameter, e.g.
rootflags=data=journal.journal
All data is committed into the journal prior to being
written into the main file(1,n) system.
ordered
This is the default mode. All data is forced directly
out to the main file(1,n)system prior to its metadata being
committed to the journal.
writeback
Data ordering is not preserved - data may be written into
the main file(1,n)systemafter its metadata has been commit-
ted to the journal. This is rumoured to be the highest-
throughput option. It guarantees internal file(1,n)system
integrity, however it can allow old data to appear in(1,8)
files after a crash and journal recovery.
commit=nrsec
Sync all data and metadata every nrsec seconds. The default
value is 5 seconds. Zero means default.
Mount optionsfor fat
(Note: fat is not a separate filesystem, but a common part of the
msdos, umsdos and vfat filesystems.)
blocksize=512 / blocksize=1024 / blocksize=2048
Set blocksize (default 512).uid=value and gid=value
Set the owner and group of all files. (Default: the uid and gid
of the current process.)
umask=value
Set the umask (the bitmask of the permissions that are not
present). The default is the umask of the current process. The
value is given in(1,8) octal.
dmask=value
Set the umask applied to directories only. The default is the
umask of the current process. The value is given in(1,8) octal.
fmask=value
Set the umask applied to regular files only. The default is the
umask of the current process. The value is given in(1,8) octal.
check=value
Three different levels of pickyness can be chosen:
r[elaxed]
Upper and lowercase are accepted and equivalent, long
name parts are truncated (e.g. verylongname.foobar
becomes verylong.foo), leading and embedded spaces are
accepted in(1,8) each name part (name and extension).n[ormal]
Like "relaxed", but many special characters (*, ?, <,
spaces, etc.) are rejected. This is the default.
s[trict]
Like "normal", but names may not contain long parts and
special characters that are sometimes used on Linux, but
are not accepted by MS-DOS are rejected. (+, =, spaces,
etc.)
codepage=value
Sets the codepagefor converting to shortname characters on FAT
and VFAT filesystems. By default, codepage 437 is used.
conv=b[inary] / conv=t[ext] / conv=a[uto]
The fatfile(1,n)system can perform CRLF<-->NL (MS-DOS textformat
to UNIX textformat) conversion in(1,8) the kernel. The following
conversion modes are available:
binaryno translation is performed. This is the default.
textCRLF<-->NL translation is performed on all files.
auto(5,8)CRLF<-->NL translation is performed on all files that
don't have a "well-known binary" extension. The list of
known extensions can be found at the beginning of
fs/fat/misc.c (as of 2.0, the list is: exe, com, bin,
app, sys, drv, ovl, ovr, obj, lib, dll, pif, arc, zip,
lha(1,n), lzh, zoo, tar, z, arj, tz, taz, tzp, tpz, gz, tgz,
deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl,
dvi).
Programs that do computed lseeks won't like in-kernel text con-
version. Several people have had their data ruined by this
translation. Beware!
For file(1,n) systems mounted in(1,8)binary mode, a conversion tool
(fromdos/todos) is available.
cvf_format=module
Forces the driver to use the CVF (Compressed Volume File) module
cvf_module instead of auto-detection. If the kernel supports
kmod, the cvf_format=xxx option also controls on-demand CVF mod-
ule loading.
cvf_option=option
Option passed to the CVF module.
debug Turn on the debug flag. A version(1,3,5)string(3,n) and a list of file(1,n)system parameters will be printed (these data are also printed
if(3,n) the parameters appear to be inconsistent).fat=12 / fat=16 / fat=32
Specify a 12, 16 or 32 bit fat. This overrides the automatic
FAT type detection routine. Use with caution!
iocharset=value
Character set(7,n,1 builtins) to use for converting between 8 bit characters and
16 bit Unicode characters. The default is iso8859-1. Long file-
names are stored on disk in(1,8)Unicode format.
quiet Turn on the quiet flag. Attempts to chown(1,2) or chmod(1,2) files do not
return errors, although they fail. Use with caution!
sys_immutable, showexec, dots, nodots, dotsOK=[yes|no]
Various misguided attempts to force Unix or DOS conventions onto
a FAT file(1,n) system.
Mount optionsforhfscreator=cccc, type=cccc
Set the creator/type values as shown by the MacOS finder used
for creating new files. Default values: '????'.uid=n, gid=n
Set the owner and group of all files. (Default: the uid and gid
of the current process.)
dir_umask=n, file_umask=n, umask=n
Set the umask used for all directories, all regular files, or
all files and directories. Defaults to the umask of the current
process.
session=n
Select the CDROM session to mount. Defaults to leaving that
decision to the CDROM driver. This option will fail with any-
thing but a CDROM as underlying device.
part=n Select partition number n from the device. Only makes sense for
CDROMS. Defaults to not parsing the partition table at all.
quiet Don't complain about invalid mount(2,8) options.
Mount optionsfor hpfsuid=value and gid=value
Set the owner and group of all files. (Default: the uid and gid
of the current process.)
umask=value
Set the umask (the bitmask of the permissions that are not
present). The default is the umask of the current process. The
value is given in(1,8) octal.
case=lower/ case=asis
Convert all files names to lowercase, or leave them. (Default:
case=lower.)
conv=binary/ conv=text/ conv=auto(5,8)
For conv=text, delete some random(3,4,6) CRs (in(1,8) particular, all fol-
lowed by NL) when reading a file. For conv=auto(5,8), choose more or
less(1,3)atrandom(3,4,6) between conv=binaryand conv=text. For
conv=binary, just read(2,n,1 builtins) what is in(1,8) the file. This is the default.
nocheck
Do not abort(3,7) mounting when certain consistency checks fail.
Mount optionsfor iso9660
ISO 9660 is a standard describing a filesystem structure to be used on
CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
udf filesystem.)
Normal iso9660 filenames appear in(1,8) a 8.3 format (i.e., DOS-like
restrictions on filename length), and in(1,8) addition all characters are in(1,8)
upper case. Also there is no field forfile(1,n)ownership, protection,
number of links, provision for block/character devices, etc.
Rock Ridge is an extension to iso9660 that provides all of these unix
like features. Basically there are extensions to each directory record
that supply all of the additional information, and when Rock Ridge is
in(1,8) use, the filesystem is indistinguishable from a normal UNIX file(1,n)system (except that it is read-only, of course).norock Disable the use of Rock Ridge extensions, even if(3,n) available. Cf.
map.nojoliet
Disable the use of Microsoft Joliet extensions, even if(3,n) avail-
able. Cf. map.check=r[elaxed] / check=s[trict]
With check=relaxed, a filename is first converted to lowercase
before doing the lookup. This is probably only meaningful
together with norock and map=normal. (Default: check=strict.)
uid=value and gid=value
Give all files in(1,8) the file(1,n)system the indicated user or groupid, possibly overriding the information found in(1,8) the Rock Ridge
extensions. (Default: uid=0,gid=0.)
map=n[ormal] / map=o[ff] / map=a[corn]
For non-Rock Ridge volumes, normal name translation maps upper
to lowercase ASCII, drops a trailing `;1', and converts `;' to
`.'. With map=off no name translation is done. See norock.
(Default: map=normal.) map=acorn is like map=normal but also
apply Acorn extensions if(3,n) present.
mode=value
For non-Rock Ridge volumes, give all files the indicated mode.
(Default: read(2,n,1 builtins) permission for everybody.) Since Linux 2.1.37
one no longer needs to specify the mode in(1,8) decimal. (Octal is
indicated by a leading 0.)
unhide Also show hidden and associated files. (If the ordinary files
and the associated or hidden files have the same filenames, this
may make the ordinary files inaccessible.)
block=[512|1024|2048]
Set the block size to the indicated value. (Default:
block=1024.)
conv=a[uto] / conv=b[inary] / conv=m[text] / conv=t[ext]
(Default: conv=binary.) Since Linux 1.3.54 this option has no
effect anymore. (And non-binary settings used to be very dan-
gerous, possibly leading to silent data corruption.)
cruft If the high byte of the file(1,n) length contains other garbage, set(7,n,1 builtins)
this mount(2,8)option to ignore the high order bits of the file(1,n)
length. This implies that a file(1,n) cannot be larger than 16MB.
session=x
Select number of session on multisession CD. (Since 2.3.4.)
sbsector=xxx
Session begins from sector xxx. (Since 2.3.4.)
The following options are the same asfor vfat and specifying them only
makes sense when using discs encoded using Microsoft's Joliet exten-
sions.
iocharset=value
Character set(7,n,1 builtins) to use for converting 16 bit Unicode characters on
CD to 8 bit characters. The default is iso8859-1.
utf8Convert 16 bit Unicode characters on CD to UTF-8.
Mount optionsfor jfsiocharset=name
Character set(7,n,1 builtins) to use for converting from Unicode to ASCII. The
default is to do no conversion. Use iocharset=utf8for UTF8
translations. This requires CONFIG_NLS_UTF8 to be set(7,n,1 builtins)in(1,8) the
kernel .config file.
resize=value
Resize the volume to value blocks. JFS only supports growing a
volume, not shrinking it. This option is only valid during a
remount, when the volume is mounted read-write. The resize key-
word with no value will grow the volume to the fullsize of the
partition.
nointegrity
Do not write(1,2) to the journal. The primary use of this option is
to allow for higher performance when restoring a volume from
backup media. The integrity of the volume is not guaranteed if(3,n)
the system abnormally abends.
integrity
Default. Commit metadata changes to the journal. Use this
option to remount a volume where the nointegrity option was pre-
viously specified in(1,8) order to restore normal behavior.
errors=continue/ errors=remount-ro / errors=panic
Define the behaviour when an error(8,n) is encountered. (Either
ignore errors and just mark the file(1,n)system erroneous and con-
tinue, or remount the file(1,n)system read-only, or panic and halt
the system.)
noquota / quota(1,8)/ usrquota / grpquota
These options are accepted but ignored.
Mount optionsfor minix
None.
Mount optionsfor msdos
See mount(2,8)optionsfor fat. If the msdosfile(1,n)system detects an incon-
sistency, it reports an error(8,n) and sets the file(1,n)system read-only. The
file(1,n)system can be made writeable again by remounting it.
Mount optionsfor ncpfs
Just like nfs, the ncpfs implementation expects a binary argument (a
structncp_mount_data) to the mount(2,8)system call. This argument is con-
structed by ncpmount(8) and the current version(1,3,5) of mount(2,8)(2.12) does
not know anything about ncpfs.
Mount optionsfornfs
Instead of a textual optionstring(3,n), parsed by the kernel, the nfsfile(1,n)system expects a binary argument of typestructnfs_mount_data. The
program mount(2,8)itself parses the following options of the form
`tag=value', and puts(3,n) them in(1,8) the structure mentioned: rsize=n,wsize=n,timeo=n,retrans=n,acregmin=n,acregmax=n,acdirmin=n,acdirmax=n,actimeo=n,retry=n,port=n,mountport=n,mounthost=name,mountprog=n,mountvers=n,nfsprog=n,nfsvers=n,namlen=n. The optionaddr=n is accepted but ignored. Also the following Boolean options,
possibly preceded by no are recognized: bg, fg, soft, hard, intr,
posix, cto, ac, tcp, udp, lock. For details, see nfs(5).
Especially useful options include
rsize=8192,wsize=8192
This will make your nfs connection faster than with the default
buffersize of 4096. (NFSv2 does not work with larger values of
rsize and wsize.)
hard The program accessing a file(1,n) on a NFS mounted file(1,n)system will
hang when the server crashes. The process cannot be interrupted
or killed unless you also specify intr. When the NFS server is
back online the program will continue undisturbed from where it
was. This is probably what you want.
soft This option allows the kernel to time(1,2,n) out if(3,n) the nfs server is
not responding for some time. The time(1,2,n) can be specified with
timeo=time(1,2,n). This option might be useful if(3,n) your nfs server
sometimes doesn't respond or will be rebooted while some process
tries to get a file(1,n) from the server. Usually it just causes
lots of trouble.
nolock Do not use locking. Do not start lockd.
Mount optionsfor ntfsiocharset=name
Character set(7,n,1 builtins) to use when returning file(1,n) names. Unlike VFAT,
NTFS suppresses names that contain unconvertible characters.
Deprecated.
nls=name
New name for the option earlier called iocharset.utf8Use UTF-8for converting file(1,n) names.
uni_xlate=[0|1|2]
For 0 (or `no' or `false'), do not use escape sequences forunknownUnicode characters. For 1 (or `yes' or `true') or 2,
use vfat-style 4-byte escape sequences starting with ":". Here 2
give a little-endian encoding(3,n) and 1 a byteswapped bigendian
encoding.
posix=[0|1]
If enabled (posix=1), the file(1,n)system distinguishes between
upper and lower case. The 8.3 alias names are presented as hard
links instead of being suppressed.
uid=value, gid=value and umask=value
Set the file(1,n) permission on the filesystem. The umask value is
given in(1,8) octal. By default, the files are owned by root and not
readable by somebody else.
Mount optionsforproc(5,n)uid=value and gid=value
These options are recognized, but have no effect as far as I can
see.
Mount optionsfor ramfs
Ramfs is a memory based filesystem. Mount it and you have it. Unmount
it and it is gone. Present since Linux 2.3.99pre4. There are no mount(2,8)
options.
Mount optionsforreiserfs
Reiserfs is a journaling filesystem. The reiserfsmount(2,8)options are
more fully described athttp://www.namesys.com/mount-options.html.conv Instructs version(1,3,5) 3.6 reiserfs software to mount(2,8) a version(1,3,5) 3.5
file(1,n)system, using the 3.6 formatfor newly created objects.
This file(1,n)system will no longer be compatible with reiserfs 3.5
tools.
hash=rupasov / hash=tea / hash=r5 / hash=detect
Choose whichhash function reiserfs will use to find files
within directories.
rupasov
A hash invented by Yury Yu. Rupasov. It is fast and pre-
serves locality, mapping lexicographically close(2,7,n)file(1,n)
names to close(2,7,n)hash values. This option should not be
used, as it causes a high probability of hash collisions.
tea A Davis-Meyer function implemented by Jeremy
Fitzhardinge. It uses hash permuting bits in(1,8) the name.
It gets(3,n) high randomness and, therefore, low probability
of hash collisions at some CPU cost. This may be used if(3,n)
EHASHCOLLISION errors are experienced with the r5 hash.
r5 A modified version(1,3,5) of the rupasov hash. It is used by
default and is the best choice unless the file(1,n)system has
huge directories and unusual file-name patterns.
detect Instructs mount(2,8) to detect whichhash function is in(1,8) use
by examining the file(1,n)system being mounted, and to write(1,2)
this information into the reiserfs superblock. This is
only useful on the first mount(2,8) of an old formatfile(1,n) sys-
tem.
hashed_relocation
Tunes the block allocator. This may provide performance improve-
ments in(1,8) some situations.
no_unhashed_relocation
Tunes the block allocator. This may provide performance improve-
ments in(1,8) some situations.
noborder
Disable the border allocator algorithm invented by Yury Yu.
Rupasov. This may provide performance improvements in(1,8) some sit-
uations.
nolog Disable journalling. This will provide slight performance
improvements in(1,8) some situations at the cost of losing reiserfs's
fast recovery from crashes. Even with this option turned on,
reiserfs still performs all journalling operations, save for
actual writes into its journalling area. Implementation of
nolog is a work in(1,8) progress.
notail By default, reiserfs stores small files and `file(1,n) tails'
directly into its tree. This confuses some utilities such asLILO(8).This option is used to disable packing of files into
the tree.
replayonly
Replay the transactions which are in(1,8) the journal, but do not
actually mount(2,8) the file(1,n) system. Mainly used by reiserfsck.resize=number
A remount optionwhich permits online expansion of reiserfs par-
titions. Instructs reiserfs to assume that the device has num-ber blocks. This option is designed for use with devices which
are under logical volume management (LVM). There is a special
resizer utility which can be obtained from
ftp://ftp.namesys.com/pub/reiserfsprogs.Mount optionsfor romfs
None.
Mount optionsfor smbfs
Just like nfs, the smbfs implementation expects a binary argument (a
structsmb_mount_data) to the mount(2,8)system call. This argument is con-
structed by smbmount(8) and the current version(1,3,5) of mount(2,8)(2.12) does
not know anything about smbfs.
Mount optionsfor sysv
None.
Mount optionsfor tmpfs
The following parameters accept(2,8) a suffix k, m or g for Ki, Mi, Gi
(binarykilo, mega and giga) and can be changed on remount.
size=nbytes
Override default maximum size of the filesystem. The size is
given in(1,8)bytes, and rounded down to entire pages. The default
is half of the memory.
nr_blocks=
Set number of blocks.
nr_inodes=
Set number of inodes.
mode= Set initial permissions of the root directory.
Mount optionsfor udf
udf is the "Universal Disk Format" filesystem defined by the Optical
Storage Technology Association, and is often used for DVD-ROM. See
also iso9660.gid= Set the default group.
umask= Set the default umask. The value is given in(1,8) octal.
uid= Set the default user.
unhide Show otherwise hidden files.
undelete
Show deleted files in(1,8) lists.
nostrict
Unset strict conformance.
iocharset
Set the NLS character set.
bs= Set the block size. (May not work unless 2048.)
novrs Skip volume sequence recognition.
session=
Set the CDROM session counting from 0. Default: last session.
anchor=
Override standard anchor location. Default: 256.
volume=
Override the VolumeDesc location. (unused)
partition=
Override the PartitionDesc location. (unused)
lastblock=
Set the last block of the filesystem.
fileset=
Override the fileset block location. (unused)
rootdir=
Override the root directory location. (unused)
Mount optionsfor ufsufstype=value
UFS is a file(1,n)system widely used in(1,8) different operating systems.
The problem are differences among implementations. Features of
some implementations are undocumented(2,3), so its hard to recognize
the type of ufs automatically. That's why the user must specify
the type of ufs by mount(2,8) option. Possible values are:
old Old format of ufs, this is the default, read(2,n,1 builtins) only.
(Don't forget to give the -r option.)
44bsd For filesystems created by a BSD-like system
(NetBSD,FreeBSD,OpenBSD).sun For filesystems created by SunOS or Solaris on Sparc.
sunx86 For filesystems created by Solaris on x86.
hp For filesystems created by HP-UX, read-only.
nextstep
For filesystems created by NeXTStep (on NeXT station)
(currently read(2,n,1 builtins) only).nextstep-cd
For NextStep CDROMs (block_size == 2048), read-only.
openstep
For filesystems created by OpenStep (currently read(2,n,1 builtins)
only). The same filesystem type is also used by Mac OS
X.
onerror=value
Set behaviour on error:
panicIf an error(8,n) is encountered, cause a kernel panic.
[lock|umount|repair]
These mount(2,8)options don't do anything at present; when an
error(8,n) is encountered only a console(4,n)message is printed.
Mount optionsfor umsdos
See mount(2,8)optionsfor msdos. The dotsOK option is explicitly killed by
umsdos.Mount optionsfor vfat
First of all, the mount(2,8)optionsforfat are recognized. The dotsOKoption is explicitly killed by vfat. Furthermore, there are
uni_xlateTranslate unhandled Unicode characters to special escaped
sequences. This lets you backup and restore filenames that are
created with any Unicode characters. Without this option, a '?'
is used when no translation is possible. The escape character is
':' because it is otherwise illegal on the vfat filesystem. The
escape sequence that gets(3,n) used, where u is the unicode charac-
ter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).posix Allow two files with names that only differ in(1,8) case.
nonumtail
First try to make a short name without sequence number, before
trying name~num.ext.utf8UTF8 is the filesystem safe 8-bit encoding(3,n) of Unicode that is
used by the console. It can be be enabled for the filesystem
with this option. If `uni_xlate' gets(3,n)set(7,n,1 builtins), UTF8 gets(3,n) disabled.
shortname=[lower|win95|winnt|mixed]
Defines the behaviour for creation and display of filenames
which fit into 8.3 characters. If a long name for a file(1,n) exists,
it will always be preferred display. There are four modes:
lower Force the short name to lowercase upon display; store a
long name when the short name is not all upper case.
win95 Force the short name to upper case upon display; store a
long name when the short name is not all upper case.
winnt Display the shortname as is; store a long name when the
short name is not all lowercase or all upper case.
mixed Display the short name as is; store a long name when the
short name is not all upper case.
The default is "lower".Mount optionsfor usbfsdevuid=uid and devgid=gid and devmode=mode
Set the owner and group and mode of the device files in(1,8) the
usbfs file(1,n)system (default: uid=gid=0, mode=0644). The mode is
given in(1,8) octal.
busuid=uid and busgid=gid and busmode=mode
Set the owner and group and mode of the bus directories in(1,8) the
usbfs file(1,n)system (default: uid=gid=0, mode=0555). The mode is
given in(1,8) octal.
listuid=uid and listgid=gid and listmode=mode
Set the owner and group and mode of the file(1,n)devices (default:
uid=gid=0, mode=0444). The mode is given in(1,8) octal.
Mount optionsfor xenix
None.
Mount optionsforxfsbiosize=size
Sets the preferred buffered I/Osize (default size is 64K).size must be expressed as the logarithm (base2) of the desired
I/O size. Valid values for this option are 14 through 16,
inclusive (i.e. 16K, 32K, and 64K bytes). On machines with a 4K
pagesize, 13 (8K bytes) is also a valid size. The preferred
buffered I/Osize can also be altered on an individual file(1,n)
basis using the ioctl(2) system call.
dmapi / xdsm
Enable the DMAPI (Data Management API) event callouts.
logbufs=value
Set the number of in-memory log buffers. Valid numbers range
from 2-8 inclusive. The default value is 8 buffers forfilesys-
tems with a blocksize of 64K, 4 buffers forfilesystems with a
blocksize of 32K, 3 buffers forfilesystems with a blocksize of
16K, and 2 buffers for all other configurations. Increasing the
number of buffers may increase performance on some workloads at
the cost of the memory used for the additional log buffers and
their associated control structures.
logbsize=value
Set the size of each in-memory log buffer. Valid sizes are
16384 (16K) and 32768 (32K). The default value for machines
with more than 32MB of memory is 32768, machines with less(1,3)mem-
ory use 16384 by default.
logdev=device and rtdev=device
Use an external log (metadata journal) and/or real-time device.
An XFS filesystem has up to three parts: a data section, a log
section, and a real-time section. The real-time section is
optional, and the log section can be separate from the data sec-
tion or contained within it. Refer to xfs(5).noalign
Data allocations will not be aligned at stripe unit boundaries.
noatimeAccess timestamps are not updated when a file(1,n) is read.
norecovery
The filesystem will be mounted without running log recovery. If
the filesystem was not cleanly unmounted, it is likely to be
inconsistent when mounted in(1,8)norecovery mode. Some files or
directories may not be accessible because of this. Filesystems
mounted norecovery must be mounted read-only or the mount(2,8) will
fail.
nouuid Ignore the filesystem uuid. This avoids errors for duplicate
uuids.
osyncisdsync
Make writes to files opened with the O_SYNC flag set(7,n,1 builtins) behave asif(3,n) the O_DSYNC flag had been used instead. This can result in(1,8)
better performance without compromising data safety. However if(3,n)
this option is in(1,8) effect, timestamp updates from O_SYNC writes
can be lost if(3,n) the system crashes.
quota(1,8)/ usrquota / uqnoenforce
User disk quota(1,8) accounting enabled, and limits (optionally)
enforced.
grpquota / gqnoenforce
Group disk quota(1,8) accounting enabled and limits (optionally)
enforced.
sunit=value and swidth=value
Used to specify the stripe unit and width for a RAID device or a
stripe volume. value must be specified in(1,8) 512-byte block units.
If this option is not specified and the filesystem was made on a
stripe volume or the stripe width or unit were specified for the
RAID deviceatmkfstime(1,2,n), then the mount(2,8)systemcall will
restore the value from the superblock. For filesystems that are
made directly on RAID devices, these options can be used to
override the information in(1,8) the superblock if(3,n) the underlying
disk layout changes after the filesystem has been created. The
swidth option is required if(3,n) the sunit option has been speci-
fied, and must be a multiple of the sunit value.
Mount optionsfor xiafs
None. Although nothing is wrong with xiafs, it is not used much, and is
not maintained. Probably one shouldn't use it. Since Linux version(1,3,5)
2.1.21 xiafs is no longer part of the kernel source.
THE LOOP DEVICE
One further possible type is a mount(2,8) via the loop device. For example,
the commandmount(2,8) /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024
will set(7,n,1 builtins) up the loop device/dev/loop3 to correspond to the file(1,n)/tmp/fdimage, and then mount(2,8) this device on /mnt.
This type of mount(2,8) knows about three options, namely loop, offset and
encryption, that are really options to losetup(8). (These options can
be used in(1,8) addition to those specific to the filesystem type.)
If no explicit loop device is mentioned (but just an option `-o loop'
is given), then mount(2,8)will try to find some unused loop device and use
that. If you are not so unwise as to make/etc/mtab a symbolic link(1,2) to
/proc(5,n)/mounts then any loop device allocated by mount(2,8)will be freed by
umount. You can also free a loop device by hand, using `losetup -d',
see losetup(8).RETURN CODESmount(2,8)has the following return codes (the bits can be ORed):0 success
1 incorrect invocation or permissions
2 systemerror(8,n) (out of memory, cannot fork, no more loop devices)
4 internal mount(2,8)bug or missing nfssupport in(1,8)mount(2,8)8 user interrupt
16 problems writing or locking /etc/mtab
32 mount(2,8) failure
64 some mount(2,8) succeeded
FILES/etc/fstabfile(1,n)system table
/etc/mtab table of mounted file(1,n) systems
/etc/mtab~lockfile(1,n)/etc/mtab.tmp temporary file(1,n)/etc/filesystems a list of filesystem types to try
SEE ALSOmount(2,8)(2), umount(2), fstab(5), umount(8), swapon(2,8)(8), nfs(5), xfs(5),
e2label(8), xfs_admin(8), mountd(8), nfsd(8), mke2fs(8), tune2fs(8),
losetup(8)
BUGS
It is possible for a corrupted file(1,n)system to cause a crash.
Some Linux file(1,n) systems don't support -o sync(1,2,8) and -o dirsync (the ext2
and ext3 file(1,n) systems do support synchronous updates (a la BSD) when
mounted with the sync(1,2,8)option).
The -o remount may not be able to change mount(2,8) parameters (all ext2fs-
specific parameters, except sb, are changeable with a remount, for
example, but you can't change gid or umaskfor the fatfs).
Mount by label or uuid will work only if(3,n) your devices have the names
listed in(1,8)/proc(5,n)/partitions. In particular, it may well fail if(3,n) the
kernel was compiled with devfs but devfs is not mounted.
HISTORY
A mount(2,8)command existed in(1,8) Version 5 AT&T UNIX.
Linux 2.6 2004-12-16 MOUNT(8)